We propose to test the hypothesis that time-varying (AC) magnetic fields interact with biological systems in a fundamentally different way if a static (DC) magnetic field is present. The Lednev paramagnetic resonance theory predicts that the frequency, intensity, and orientation of the AC field, and the intensity and orientation of the DC field must all be rigorously controlled and varied in a specific manner in order to observe conforming to this theory significantly decreased mitogen-activated calcium transport in rat lymphocytes, and that AC and DC fields alone had no effect [1.8 AC/DC intensity ratio, 231mG DC, 16Hz AC for Ca2+, Yost & Liburdy, 1992]. Resting cells did not respond to this AC/DC field combination indicating that calcium signaling is important. Preliminary data show that Ca2+ influx is decreased or increased as the AC/DC field ratio is varied according to parametric theory. This is supported by the first real time fluorescence measurements of [Ca+2] for Con-A activated rat thymocyte during AC/DC field exposures [1.8 AC/DC]; the plateau phase of [Ca+2] fluorescence measurements of [Ca+2]i and [pH]i during AC/DC field exposure in the presence of a second mitogen, TPA, and both are markedly diminished at the same field conditions [1.8 AC/DC] where an effect is predicted. The above data, obtained using different exposure systems, mitogens, and calcium assays, are consistent with Lednev theory, and strongly implicate calcium and the cell membrane as an interaction site. The primary hypothesis we will test, therefore, is that specific AC/DC field combinations increase or decrease calcium signaling in mitogen- activated thymocyte according to Lednev parametric theory. While monitoring [Ca+2]i, and [pH]i, we will systematically vary the AC/DC field intensity ratio, conduct separate AC and DC field exposures, and vary the frequency of the AC field according to theory. Results will be correlated across three different exposure systems for cells exposed in a cuvette, a microtitre plate, or a microscope perfusion chamber. Each system can address different questions, and this is a major strength of the study. Mechanism studies will test calcium ion blocking and substitution, and mitogen binding. A secondary hypothesis we will test is that AC/DC field combination which increase or decrease calcium influx may increase or decrease cell viability/proliferation, respectively. A significant increase in viable cells in seen during co-culture with Con-A, with PHA, or with a MAb directed against the T-cell receptor, in the presence of AC?DC fields that increase calcium influx [5.3 AC/DC intensity ratio, 231mG DC, 16Hz AC]. This is consistent with calcium signaling in mitogen-activated thymocyte. Selected AC/DC fields ratios that alter calcium signalling will be tested for changes in cell viability and cell proliferation (DNA synthesis).